Viruses Complex Molecules Or Simple Life Forms

Viruses: Complex Molecules Or Simple Life Forms? Essay, Research Paper

Viruses: Complex Molecules or Simple Life Forms?

Viruses have been defined as “entities whose genomes are elements of

nucleic acid that replicate inside living cells using the cellular synthetic

machinery, and cause the synthesis of specialised elements that can transfer the

genome to other cells.” They are stationaryand are unable to grow. Because of

all these factors, it is debatable whether viruses are the most complex of

molecules or the simplest life forms. While the definition of living organisms

must be adapted, the majority of evidence leads to the classification of viruses

as living organisms.

Viruses are composed of a nucleic acid core, a protein capsid, and

occasionally a membraneous envelope. The nucleic acid core is composed of

either DNA or in the case of retroviruses, RNA, but never both. In retroviruses,

the RNA gets transcribed to DNA bye the enzyme reverse transcriptase. The

protein capsid is a protein layer that wraps around the virus. There are four

basic shapes of viruses. The tobacco mosiac, adenovirus, influenza virus, and

t-even bacteriophage are each examples of a different virus structure. Each

individual protein subunit composing the capsid is a capsomere.

The tobacco mosiac virus has a helical capsoid and is rod shaped. The

adenovirus is polyhedral and has a protein spike at each vertex. The influenza

virus is made of a flexible, helecal capsid. It has an outer membranous

enevelope that is covered with glycoprotein spikes. The T-even bacteriophage

consists of a polyhedral head and a tail. The tail is used to inject DNA into a

bacterium while the head stores the DNA.

Basic life is defined as the simplest form capable of displaying the

most essential attributes of a living thing. This makes the only real criterion

for life the ability to replicate. Only systems containing nucleic acids are

capable of this phenomenon. With this reasoning, a better definition is the

unit element of a continuous lineage with an individual evolutionary history.

Because of viruses inability to survive when not in a host, they must have

evolved from other forms of life. The origin of viruses is an easy thing to

theorize about so many hypothesese have been made.

One such hypothesis is that viruses were once complete living parasites.